The invention relates to a threaded syringe. More particularly, this invention relates to a syringe for use in the delivery of a bone substitute material.
Injectable bone substitute materials are used for the repair and augmentation of orthopedic fractures and defects. Bone substitute materials can also be used in certain diagnostic or therapeutic procedures that require the formation of a cavity in a bone mass. This procedure can be used to treat any bone, for example, bone which due to osteoporosis, avascular necrosis, cancer, or trauma, is fractured or is prone to compression fracture or collapse. These conditions, if not successfully treated, can result in deformities, chronic complications, and an overall adverse impact upon the quality of life.
Furthermore, it is known that during some surgical operations, it is necessary to inject a relatively large quantity of bone substitute material at relatively low pressure and thereafter to inject a small quantity of material at relatively high pressure without applying substantially increased force. However, especially with highly viscous or solid, yet pliable cement compositions, it is often difficult with a standard push-type syringe to generate the pressure needed to express the material through the syringe outlet opening by exerting pressure on the syringe plunger in an axial direction. Another serious problem is that once sufficient pressure is applied to the plunger, it is difficult to precisely control the amount of material expelled through the outlet opening of the barrel, resulting in extraosseous (i.e., outside the bony cavity) flow.
Various types of devices have been used for delivering bone substitute material, such as bone cement. For example, injector guns having a trigger mechanism that includes a trigger in the form of a lever have been used. Also, standard push-type syringes comprising a barrel and a plunger may be used for such purposes.
A bone cement gun is described in U.S. Pat. No. 5,638,997 as having a trigger mechanism that has first and second mechanical advantages corresponding to the trigger stroke. The first mechanical advantage facilitates generating a high pressure in the U.S. Pat. No. 4,338,925, a trigger gun is disclosed that utilizes a trigger mechanism with a constant mechanical advantage.
Trigger guns, however, generally lack the improved tactile feedback available using a syringe apparatus. Such improved tactile feedback is important to notify the surgeon when there is an occlusion or other blockage which prevents the material from exiting the delivery device, or in the performance of sensitive procedures such as in repair of the vertebra.
One type of injector or syringe for injecting bone cement into surgically prepared bone cavities is described in European Patent B 1-006430. The bone cement injector consists of a piston and cylindrical tube to which a nozzle element having a nozzle tube of relatively narrow cross-section is attached. Such an injector is constructed so as to permit the mixing and extrusion of a pasty bone cement in a simple manner. In this regard, the nozzle tube is made as a two-part member of relatively narrow cross-section.
Another type of syringe for bone cement is described in U.S. Pat. No. 4,576,152. The injector is provided with an injection nozzle in the bottom of the cylinder tube for low pressure operation to deliver large quantities of bone cement. A nozzle element can be releasably attached to the cylinder tube for high pressure injection. The nozzle element is removed for low pressure injection and attached for high pressure injection.
The invention relates to a syringe for delivery of a bone substitute material. The syringe includes a barrel for holding the material, a plunger receivable within the barrel and having a threaded portion, and an engagement member including a threaded throughbore positioned coaxial with the barrel. The threaded portion of the plunger is movable through the threaded throughbore barrel by pushing the plunger in the axial direction, and by rotating the plunger.
The preferred engagement member has a C-shape and includes a slot extending radially therethrough. In addition, the preferred engagement member is expandable in the radial direction. In one embodiment, the cross-sectional area of the throughbore is variable. In another embodiment, the throughbore includes an inner surface that is in full contact with the plunger when the plunger moves therethrough.
In another preferred embodiment, the material exits the barrel under a first pressure when the plunger is pushed in the distal direction and the material exits the barrel under a second pressure when the plunger is advanced through rotation. Preferably, an audible noise is made as the threaded portion plunger moves past the engagement member when the plunger is pushed in the axial direction. Preferably, a predetermined amount of material is expelled from the barrel with each audible click. In addition, a predetermined amount of material is expelled from the barrel when the barrel is advanced with each rotation of the plunger.
Preferably, the syringe also includes a coupling member configured to receive a portion of a package containing material to facilitate the transfer of material from the package to the barrel. The preferred coupling member includes a funnel member to funnel the material into the barrel.
Preferably, the syringe also includes a finger grip coupled to the barrel at the proximal end and the engagement member is housed within the finger grip. In one embodiment, the finger grip comprises a pair of half shells. In the preferred embodiment, the engagement member is movable within the finger grip between a first position to allow the plunger to advance by pushing the plunger in the axial direction and a second position to allow the plunger to advance by rotating the plunger. The preferred engagement member includes an extension arm that contacts the inner wall of the finger grip when the engagement member is in the first position. Preferably, the engagement member engages a seat for preventing the engagement member from expanding when the engagement member is in the second position.
The invention also relates to a method of expelling material from a syringe having a barrel with an engagement member, and a plunger. A preferred method includes the step of moving the plunger within the barrel by pushing the plunger through the engagement member and moving the plunger within the barrel by rotating the plunger through the engagement member.